Distort (transform) Mesh by formula
wouldn't a simple script work for you, something like this:

import bpy  
obj = bpy.context.object  
verts = obj.data.vertices  
for v in verts:  
    x,y,z = v.co[:]  
    v.co = (x+0.1*y*y, y-0.1*x*z, z+0.1*z*x)